Alternative for estimating the burden of lung cancer from occupational exposures--some calculations based on data from Swedish men

OBJECTIVES: This study attempts to demonstrate a calculation of the occupational lung cancer burden using economically active men in Sweden as an example. METHODS: Estimates were calculated using Swedish register data on occupation in 1970, lung cancer incidence in 1971-1989, smoking frequencies in 1963, and the formula I = RI0F + I0(1-F), where I is the overall incidence, R is the relative risk associated with a factor (here smoking), F is the fraction of persons at risk (smokers), and I0 is the incidence among those not at risk (nonsmokers). RESULTS: Farmers, gardeners, forestry workers, and fishermen had the lowest lung cancer risk (42.1 per 100,000 person-years) and a smoking frequency of 44.7%. Their I0 was 12.6 or 8.4 per 100,000 person-years, taking R for smoking as 6 or 10, respectively. From these I0 estimates, the expected rates for white- and blue-collar workers (smoking frequencies 52.7 and 57.7%, respectively) were 45.8 and 49.1 per 100,000 person-years, as compared with the 22% and 57% higher observed rates, respectively. Weighing these excesses proportionally according to the sizes of the three occupational categories gave, respectively for R equal to 6 and 10, occupation-related excesses of 39% and 32% and population-attributable risks of 28% and 24%. CONCLUSIONS: About one-fourth of the lung cancers that occur among economically active Swedish men seem to have been related to occupation. This figure agrees with estimates made by other methods in Nordic countries. Due to interaction, the population-attributable risk from smoking is still high, 73% and 83% at relative risk values of 6 and 10, respectively.     

Cancer risk among glass factory workers: an excess of lung cancer?

A total of 3749 workers employed for at least three months in two Finnish glass factories (cohorts A and B) were followed up for cancer in 1953-86 through the Finnish Cancer Registry. In cohort A (1353 men, 1261 women), 106 primary cancers were diagnosed among men, and their standardised incidence ratio (SIR) for all cancers was 99. Among women the risk was low (65 cases, SIR 64). In cohort B (450 men, 685 women), the relative risk of cancer was close to unity for both men (57 cases) and women (75 cases). The risk of cancer was analysed by primary site, type of work, years since first exposure, and age at diagnosis. The only significantly increased risks were those of lung cancer among men (SIR 130, 95% CI 100-167, cohorts A and B combined), and skin cancer among glass blowers (SIR 625, 95% CI 129-1827). An increased risk of lung, stomach, and colon cancer as well as of brain tumours has been reported in previous studies. It is postulated that the excess risk of lung cancer, detected in this study, can also be accounted for by lifestyle, and not only by possible occupational exposures, because a similar excess risk of lung cancer has been found previously for all industrial workers in Finland. Although the risk of stomach cancer in this study was increased among glass blowers, it was not high in the largest groups of plain glass workers. The risks of tumours of the central nervous system and colon were not increased either.     

Incidence of cancer among anthophyllite asbestos miners in Finland.

A cohort of 736 male and 167 female workers of two anthophyllite mines in Finland was followed up through the Finnish Cancer Registry for cancer in 1953-91. Compared with the total cancer incidence of the east Finnish population, the men had a raised risk of total cancer (standardised incidence ratio (SIR) 1.7; 95% confidence interval (95% CI) 1.4-1.9), mainly attributable to an excess in lung cancer (SIR 2.8; 95% CI 2.2-3.6). The risk of lung cancer was somewhat higher among workers classified as heavily exposed (SIR 3.2; 95% CI 2.4-4.1) than among those moderately exposed (SIR 2.3; 95% CI 1.5-3.6) and the risk increased with increasing smoking and with increasing time of work with exposure. There were four cases of mesothelioma v 0.1 expected, all in men who smoked and had had a long and heavy asbestos exposure. Among women, a non-significant excess in total cancer (SIR 1.5; 95% CI 0.9-2.4) was found in the subgroup with heavy exposure to asbestos. Anthophyllite asbestos seems to have high potency in the carcinogenesis of lung cancer and low potency in carcinogenesis of mesothelioma in comparison with the other types of asbestos.     

Cancer risk among glass factory workers: an excess of lung cancer?

A total of 3749 workers employed for at least three months in two Finnish glass factories (cohorts A and B) were followed up for cancer in 1953-86 through the Finnish Cancer Registry. In cohort A (1353 men, 1261 women), 106 primary cancers were diagnosed among men, and their standardised incidence ratio (SIR) for all cancers was 99. Among women the risk was low (65 cases, SIR 64). In cohort B (450 men, 685 women), the relative risk of cancer was close to unity for both men (57 cases) and women (75 cases). The risk of cancer was analysed by primary site, type of work, years since first exposure, and age at diagnosis. The only significantly increased risks were those of lung cancer among men (SIR 130, 95% CI 100-167, cohorts A and B combined), and skin cancer among glass blowers (SIR 625, 95% CI 129-1827). An increased risk of lung, stomach, and colon cancer as well as of brain tumours has been reported in previous studies. It is postulated that the excess risk of lung cancer, detected in this study, can also be accounted for by lifestyle, and not only by possible occupational exposures, because a similar excess risk of lung cancer has been found previously for all industrial workers in Finland. Although the risk of stomach cancer in this study was increased among glass blowers, it was not high in the largest groups of plain glass workers. The risks of tumours of the central nervous system and colon were not increased either.     

Exposure to nickel compounds and smoking in relation to incidence of lung and nasal cancer among nickel refinery workers.

OBJECTIVES: To investigate the relation between occupational hazards among nickel refinery workers and their exposure to different forms of nickel over time and the interaction between smoking and total exposure to nickel. METHODS: The cohort consisted of 379 workers with first employment 1916-40 and at least three years of employment and 4385 workers with at least one year of employment 1946-83. Data on smoking (ever or never) were available for almost 95% of the cohort. Two analyses were used, indirect standardisation from observed and expected numbers and Poisson regression. RESULTS: During the follow up 1953-93, 203 new cases of lung cancer were observed v 68 expected (standardised incidence ratio (SIR) 3.0, 95% confidence interval (95% CI) 2.6-3.4) and 32 cases of nasal cancer were observed v 1.8 expected (SIR 18.0, 95% CI 12-25). The Poisson regression analysis showed an excess risk of lung cancer in association with exposure to soluble forms of nickel, with a threefold increase in relative risk (RR) (P < 0.001) and a multiplicative effect of smoking and exposure to nickel. The RRs were 1.1 (95% CI 0.2-5.1) for exposed workers who had never smoked and 5.1 (95% CI 1.3-20.5) for exposed workers who smoked. CONCLUSION: It is not possible to state with certainty which specific nickel compounds are carcinogenic, but a significant excess risk was found for workers exposed to soluble nickel alone or in combination with other forms of nickel. The present study suggests a multiplicative effect of smoking and nickel exposure.     

Occupational exposure to eight organic dusts and respiratory cancer among Finns

Background

There is inconclusive evidence concerning cancer risks of organic dusts.

Aim

The carcinogenic exposures are mainly inhalatory and the authors therefore studied associations between occupational exposure to eight different organic dusts and respiratory cancers in Finland.

Methods

The authors followed up a cohort of all economically active Finns born between 1906 and 1945 for 30 million person‐years during 1971–95. Incident cases of nasal, laryngeal, and lung cancer and mesotheliomas were identified through a record linkage with the Finnish Cancer Registry. Occupations from the population census in 1970 were converted to exposures to eight organic dusts with a job‐exposure matrix (FINJEM). Cumulative exposure (CE) was calculated as a product of prevalence, level, and estimated duration of exposure. Standardised incidence ratios (SIR) and 95% confidence intervals (CI) adjusted for age, period, and social class were calculated for each organic dust using the economically active population as the reference.

Results

A total of 20 426 incident cases of respiratory cancer were observed. Slightly increased risk was observed among men exposed to wood dust for nasal cancer (SIR 1.42, 95% CI 0.79 to 2.44). For laryngeal cancer, men exposed to plant dust (mainly grain millers) had a raised SIR in the high exposure class (SIR 3.55, 95% CI 1.30 to 7.72). Men exposed to wood dust had a raised SIR for lung cancer, but only in the low exposure class (SIR 1.11, 95% CI 1.04 to 1.18). Women exposed to wood dust showed an increased SIR for mesotheliomas in the low exposure class (SIR 4.57, 95% CI 1.25 to 11.7) and some excess in the medium exposure category.

Conclusions

Exposure to organic dusts is unlikely to be a major risk factor of respiratory cancer. Even exposure to wood dust which is a major exposure in Finland seems to have minor effect for nasal cancer. The authors found suggestive evidence that exposure to grain dust may increase the risk of laryngeal cancer, and some support to the hypothesis that exposure to textile dust, and to plant and animal dust (agricultural dusts) may decrease the risk of lung cancer.     

Cancers in concrete workers: results of a cohort study of 33,668 workers

OBJECTIVES—To study cancer morbidity patterns in concrete workers.
METHODS—A cohort of 33 503 concrete workers was enrolled in the study from 1971-86. The average duration of follow up was 19.4 years (582 225 person-years). The workers' cancer morbidity was compared with the morbidity of the general population.
RESULTS—A total of 3572 incident cancers were observed. Significantly increased standardised incidence ratios (SIRs) were found for all malignant neoplasms (SIR 107; 95% confidence interval (95%CI) 103 to 110), cancer of the lip (SIR 179; 95%CI 134 to 234), cancer of the stomach (SIR 139; 95%CI 122 to 158), cancer of the lung (SIR 125; 95%CI 114 to 137), and cancer of the prostate (SIR 108; 95%CI 101 to 116). Reduced risk was found for cancer of the large intestine (SIR 80; 95%CI 69 to 93) and cancer of the testis (SIR 50; 95%CI 26 to 87). Smoking was more prevalent among the concrete workers than in the general population (50% v 35%).
CONCLUSION—The study has shown a slightly increased overall risk of cancer among concrete workers. The increased risk of lung cancer could entirely be due to differences in smoking habits between concrete workers and the general population. There is a possibility that the smoking also has contributed to the increased risks of stomach cancer and lip cancer, but occupational factors may have contributed to these cancer sites.


Keywords: occupational diseases; constructions workers; smoking     

Smoking-adjusted incidence of lung cancer among Swedish men in different occupations

The Swedish Cancer-Environment Register was used to study the relation between occupation and lung cancer risk during the period 1961-79 in 1.6 million men aged 30-64 years in 1960. By adding information concerning smoking habits from a sample of 1% of the Swedish population, smoking-adjusted standardized incidence ratios (SIR) were estimated for different occupational categories according to the population census of 1960. Smoking-adjusted excess risks (p less than 0.01) were found in assemblers and machine erectors, drivers, miners, packers and longshoremen as well as in sheetmetal workers. Significantly fewer lung cancer cases than expected were seen in artists and writers, chemical and cellulose workers, farmers, farm workers, forestry workers, public administrators and in teachers. As a result of a high prevalence of smoking, the smoking-adjusted SIR was markedly lower than the unadjusted SIR in artists and writers, drivers, mechanics and repairmen, members of the armed forces and painters. The opposite situation was seen for clergy, farmers and forestry workers.     

Cancer incidence of workers in the Finnish pulp and paper industry

The cancer incidence of 3,545 workers in the Finnish pulp and paper industry was assessed in a retrospective cohort study. The cohort included workers with continuous employment of at least one year between 1 January 1945 and 31 December 1961 and was followed until 31 December 1980. Six subcohorts were formed (sulfite mill, sulfate mill, paper mill, board mill, maintenance department, and power plant). Separate analyses were made for the 2,597 workers hired after 1 January 1945. The smoking habits were surveyed. Among the men, 196 cases of primary cancer were detected versus 203.8 expected [standardized incidence ratio (SIR) 96, 95% confidence interval (95% CI) 82-114], and there were 47 cancer cases among the women versus 57.9 expected (SIR 91, 95% CI 60-108). Lung cancer occurred in 78 men (62.6 expected, SIR 125, 95% CI 98-155), and the excess was the most prominent for the male board mill workers (40 observed, 81.1 expected, SIR 222, 95% CI 158-302), particularly after 20 year's latency (25 observed, 7.8 expected, SIR 323, 95% CI 209-476). Analogous excesses of lung cancer occurred among the men (especially the male board mill workers) who began work after 1 January 1945. The findings were not explained by smoking habits.     

Cancer in printing workers in Denmark.

OBJECTIVES--To study the cancer incidence in printing workers in Denmark. METHODS--The cohort of 15,534 men and 3593 women working in the printing industry in 1970 were followed up for death, emigrations, and incident cancer cases until the end of 1987. Their cancer incidence was compared with that of all economically active people in Denmark. The smoking and drinking habits reported by members of the printing trade unions at a survey in 1972 were compared with habits reported by members of other trade unions. RESULTS--Lung, bladder, renal pelvis, and primary liver cancers were in excess among the printing workers. The excess risks of lung cancer among the factory workers in newspaper and magazine production, of bladder cancer in typographers in printing establishments, of renal pelvis cancer in typographers and lithographers, and of primary liver cancer among lithographers and bookbinders exceeded those expected based on the reported smoking and drinking habits. CONCLUSION--Our results indicate, in line with a previous study from Manchester, that work with rotary letterpress printing was associated with an increased risk of lung cancer. The inconsistent results from studies on bladder cancer in printing workers may point to a risk confined to a certain subgroup. The sixfold risk of primary liver cancer in Danish lithographers warrants studies in other countries.     

Update of cancer incidence among workers at a copper/nickel smelter and nickel refinery

Objectives: To assess cancer risk among nickel-exposed workers. Methods: We updated cancer incidence among 1388 workers employed for at least 3 months at a copper/nickel smelter and nickel refinery in Harjavalta, Finland. There were 1155 workers exposed to nickel during the period 1960–1985 in the smelter (566 workers), repair shop (239 workers), or refinery (418 workers). Cancer incidence was followed through the files of the Finnish Cancer Registry up to 31 December 1995. For overall cancer and for a priori selected specific cancer types the ratio of observed to expected numbers of cases was computed as a standardized incidence ratio (SIR), controlled for age, gender, and calendar period and using the region-specific rates as a reference. Results: The overall cancer incidence among both nickel-exposed and unexposed subcohorts was at the expected level. A small increase in lung cancer incidence, which reached statistical significance among workers with a latency exceeding 20 years, was observed among the smelter workers exposed to insoluble nickel compounds. Among workers in the refinery, who were exposed primarily to nickel sulfate at levels below 0.5 mg/m³ as well as to low concentrations of other nickel compounds, there was an increased risk for nasal cancer (SIR 41.1, 95% CI 4.97–148), positively associated with latency and duration of employment, and an excess risk for stomach (SIR 4.98, 95% CI 1.62–11.6) and lung (SIR 2.61, 95% CI 0.96–5.67) cancers. Conclusions: Since elevated nasal and lung cancer risks were confined to the refinery, where the primary exposure was to nickel sulfate, it is likely that nickel sulfate is mainly responsible for the elevated respiratory cancer risk. We cannot rule out whether the excess stomach cancer risk is a chance finding, or related to the working environment. Received: 11 September 1997 / Accepted: 17 October 1997     

Possible causes of increased lung cancer incidence among butchers and slaughterhouse workers

An excess of lung cancer among butchers and slaughterhouse workers has been reported in several record-linkage studies. In this case-referent investigation on the possibility of occupational exposures being related to the lung cancer excess, cases and referents were selected from butchers and slaughterhouse workers registered in the Swedish national census of 1960. The case group comprised all men in the study population dying from lung cancer between 1971 and 1982. Two reference groups were formed, ie, all individuals dying from other cancers and a random sample of all dead men in the study population during the same time period. The history of occupations, occupational exposures, and smoking habits was obtained from the next-of-kin by questionnaire. None of the occupational exposures that were studied (work with live animal care, in the bleeding area, on the killing floor, or with meat cutting, processing, curing, smoking, chilling and packaging) were associated with an increased lung cancer rate. Tobacco smoking habits may have contributed to the overall excess of lung cancer found previously for this occupational group.     

Study of cancer incidence among 8530 male workers in eight Norwegian plants producing ferrosilicon and silicon metal

OBJECTIVES: To examine the association between cancer incidence, in particular incidence of lung cancer, and duration of work among employees in eight Norwegian plants producing ferrosilicon and silicon metal. METHODS: Among men first employed during 1933-91 and with at least 6 months in these plants, the incident cases of cancer during 1953-91 were obtained from The Cancer Registry of Norway. The numbers of various cancers were compared with expected figures calculated from age and calendar time specific rates for Norwegian men during the same period. Internal comparisons of rates were performed with Poisson regression analysis. The final cohort comprised 8530 men. RESULTS: A total of 832 cases of cancer were observed against 786 expected (standardised incidence ratio (SIR) 1.06). Among the furnace workers an increased incidence of lung cancer (SIR 1.57) and testicular cancer (SIR 2.30) was found. Internal comparisons of rates by Poisson regression analysis among the rural furnace workers showed a positive trend between incidence of lung cancer and duration of work of 1.05 (95% confidence interval (95% CI) 1.00 to 1.10)/work-year. Excess cases of prostate and kidney cancer were found among blue collar non-furnace workers, in particular among the mechanics. CONCLUSION: The results suggest associations between furnace work and lung and testicular cancer, and between non-furnace work and prostate cancer.

 

     

Self-experienced physical workload and risk of breast cancer

OBJECTIVES: The association between the risk of breast cancer and the physical load of work was studied because physical activity may reduce breast cancer risk via hormonal mechanisms. METHODS: Occupational physical activity was estimated from a self-determined rating [scale 1 (low)-5 (high)] of occupational physical load for 1800 randomly selected women born in 1930-1969. The medians of the ratings were used as occupation-specific indices of occupational physical activity. All 65 occupations with at least 5 ratings, covering 75% of the economically active female population in Finland, were included in further analyses. The occupation-specific numbers of observed and expected cases of breast cancer during 1971-1995 among women born in 1906-1945 (17,986 cases) were grouped according to the index for occupational physical activity. Expected rates were calculated with the social-class-specific population and the entire Finnish female population as reference populations. The relative risks (RR) of breast cancer for categories 3-5, in comparison with categories 1-2 were calculated using Poisson regression models. The occupation-specific mean number of children and mean age at first childbirth were adjusted for. RESULTS: The RR was lower for occupations in category 5 than for those in categories 1-4, especially in the youngest (25-39 years) age group (RR 0.51, 95% confidence interval 0.44-0.58). Adjustment for social class and reproductive factors raised the RR (95% confidence interval 0.56-0.74) for category 5 in different age strata, all the RR values still being statistically significant. CONCLUSIONS: The results support the hypothesis that occupational physical activity, if high enough, markedly reduces breast cancer risk.     

Occupational mortality of women aged 15-59 years at death in England and Wales.

STUDY OBJECTIVE--The aim was to analyse occupational mortality differences among women using follow up data from a large nationally representative sample. DESIGN--Occupational information was obtained from the 1971 census records of women in the Longitudinal Study carried out by the Office of Population Censuses and Surveys (OPCS) and related to their subsequent mortality in the period between the 1971 and 1981 censuses. SETTING--In the Longitudinal Study, census, vital statistics, and other OPCS records are linked for a 1% sample of the population of England and Wales. The women studied in this paper were drawn from the 513,071 persons in the 1971 census who were included in the Longitudinal Study and whose entries were traced at the National Health Service Central Register by 1977. PARTICIPANTS--The analysis was based on 77,081 women aged 15-59 years in the Longitudinal Study for whom occupational information was collected in the 1971 census (99% of whom were in paid employment in the week before the census). There were 1553 deaths among these women in the follow up period analysed here. MEASUREMENTS AND MAIN RESULTS--Numbers of deaths in each occupational group at census were compared to those expected on the basis of age specific death rates among all women in the study. "Professional, technical workers, and artists" had significantly low mortality while "Engineering and allied trades workers nec" had significantly high mortality. Among the latter, cancer mortality of electrical production process workers was extremely high. A number of other cause specific associations (which appear to confirm proportionate Decennial Supplement analyses) were suggested by the data; examples include high levels of mortality from ischaemic heart disease among cooks, lung cancer and respiratory disease among charwomen and cleaners, and accidents, poisonings, and violence among several groups of professional and technical workers. CONCLUSIONS--By using prospective follow up from the census, occupational differences in mortality can be identified among women in paid employment. As follow up of this study continues, numbers of deaths available for analysis will increase, allowing increasingly comprehensive analyses to be undertaken.     

Gliomas among men employed in the Swedish pulp and paper industry

OBJECTIVES: This study investigated whether previous findings of an increased risk of gliomas among workers in some pulp and paper mills could be confirmed for all Swedish pulp and paper mill workers and whether the increase could be attributed to certain occupational groups. METHODS: The study was based on the Swedish Cancer Environment Register, which links the incidence of cancer from 1971 to 1990 and the 1960 and 1970 census data on codes of occupation and industry for the whole population. Standardized incidence ratios (SIR) were used to estimate the risks for men in different occupations in pulp (N = 28,142) and paper (N = 39,169) mills in 1960, 1970 or both years as compared with those of all gainfully employed men in Sweden. RESULTS: Maintenance workers employed in pulp or paper mills in 1960, 1970 or both years, as well aspulp workers, showed an increased incidence of gliomas in 1971-1990 [SIR 1.5, 95% confidence interval (95% CI) 1.1-2.1 and SIR 1.5,95% CI 1.0-2.2, respectively], whereas the incidence among process workers in paper mills was lower than expected (SIR 0.6, 95% CI 0.3-0.9). Taken together, all employed men in the pulp mill industry had an increased incidence of gliomas (SIR 1.3, 95% CI 1.0-1.7). CONCLUSIONS: Pulp mill workers, but not paper mill workers, were found to have more gliomas in 1971-1990 than expected. There was an increased risk of gliomas among maintenance workers in both pulp and paper mills. Few risk factors for brain tumors are recognized, and the causes of the increase are not obvious.     

Incidence of cancer among welders and other shipyard workers with information on previous work history

The incidence of cancer among 4480 shipyard workers, including 861 welders, was investigated for a potential relationship between exposure to welding fumes and lung cancer. A subcohort of 3150 workers with information on previous work history was studied separately. This investigation is a historical prospective cohort study. Environmental air samples were collected in 1973, 1977, and 1989. Information on smoking habits was surveyed in 1976 and 1984. The employment work histories were collected from the personnel register. There were 411 observed cancers of all sites versus 387.5 expected, and 45 cases of lung cancer versus 51.3 expected. Nine cases of lung cancer were found among the welders versus 7.1 expected. Among 310 former seamen with welding experience, there was 1 case of lung cancer versus 2.1 expected. These shipyard workers showed no excess risk of lung cancer. Tobacco smoking and asbestos exposure are potential confounders in the study. There was no clear relationship between exposure to welding fumes and lung cancer, but welders with the longest experience had a relative risk of 1.9 for lung cancer. The differences in lung cancer incidence among the different shipyard workers could not be attributed to differences in recruitment patterns or previous work history.     

Lung cancer and mesothelioma in the pleura and peritoneum among Swedish insulation workers

OBJECTIVES: To estimate the risk of cancer and death in Swedish insulation workers some years after their exposure to asbestos had stopped. One hypothesis was that the risk of lung cancer would tend to decrease some years after the exposure had ended. METHODS: In a cohort study the cancer morbidity and cause of death was investigated in 248 insulation workers and compared with the corresponding morbidity and mortality in the general population. Due to stringent regulations, exposure to asbestos of all types had almost ended in Sweden in the mid- 1970s. Through a questionnaire, surviving insulation workers were asked about their exposure to asbestos and their smoking habits. RESULTS: Between 1970 and 1994 there were 86 deaths compared with the 46.0 expected (standardised incidence ratio (SIR) 1.9; 95% confidence interval (95% CI) 1.5 to 2.3), the increase was mainly due to an increased cancer mortality. The morbidity was increased for lung cancer (11 cases v 2.5 expected (SIR 4.4; 95% CI 2.2 to 7.9)), peritoneal mesothelioma (seven cases; no expected incidence could be calculated as the occurrence is too rare in the general population), cancer in pancreas (five cases v 0.7 expected (SIR 7.1; 95% CI 2.3 to 16.7)). No cases of pleural mesothelioma were found. The risk of lung cancer did not tend to approach that of the general population after the exposure to asbestos decreased. CONCLUSIONS: In the 1980s and the early 1990s, Swedish insulation workers still have a highly increased risk of diseases related to asbestos. The attributable risk for death and cancer was about 50%. The study also confirms the previous finding that mesothelioma in insulation workers seems to be situated in the peritoneum more often than in the pleura.     

Incidence of cancer among bookbinders, printers, photoengravers, and typesetters

OBJECTIVES—To to study the risk of cancer, particularly of lung cancer and bladder cancer, among workers in the printing industry according to different occupations.
METHODS—This is a population based retrospective cohort study. The cohort comprised 1332 men and 426 women employed in the printing industry in Iceland according to a published union registry. A computerised file of the cohort was record linked to the Cancer Registry by making use of personal identification numbers. Expected numbers of cases of cancer were calculated on the basis of number of person-years and specific incidences of cancer sites for men and women provided by the Cancer Registry.
RESULTS—Among the men (36 217.5 person-years at risk) there were 125 observed cancers versus 123.66 expected, standardised incidence ratio (SIR) 1.01, 95% confidence interval (95% CI) was 0.84 to 1.20. The SIR (95% CI) for liver cancer was 1.97 (0.55 to 5.20) and the SIR for non-Hodgkin's lymphoma was 2.26 (0.96 to 4.41). No excess risk for cancer was found among women (8631.0 person-years at risk). The SIR (95% CI) for liver cancer was 4.21 (0.47 to 15.20) and for non-Hodgkin's lymphoma it was 4.99 (1.61 to 11.63) among the typesetters. A survey on smoking habits among active and retired union members showed that they smoked less than a random sample of the general population.
CONCLUSION—The cancer site most often reported to show excess risk among printing industry workers has been the lung and the urinary bladder; however, this was not found in the present study. This may be explained by difference in smoking habits among union members compared with the general population. There is a high occurrence of non-Hodgkin's lymphoma, particularly among typesetters, which warrants further studies.


Keywords: printing industry; non-Hodgkin's lymphoma; smoking habits     

Study of cancer incidence among 6363 male workers in four Norwegian ferromanganese and silicomanganese producing plants

OBJECTIVES: Little has been known about the risk of cancer associated with occupational exposure to manganese. The objective of this study was therefore to examine the associations between duration of specific work and cancer incidence among employees in four Norwegian ferromanganese and silicomanganese producing plants. METHODS: Among men first employed in 1933-91 and with at least 6 months in these plants, the incident cases of cancer during 1953-91 were obtained from The Cancer Registry of Norway. The numbers of various cancers were compared with expected figures calculated from age and calendar time specific rates for Norwegian men during the same period. Internal comparisons of rates were performed with Poisson regression analysis. The final cohort comprised 6363 men. RESULTS: A total of 607 cases of cancer were observed against 596 cases expected (standardised incidence ratio (SIR) 1.02). Internal comparisons of rates showed a positive trend between the rate of all cancers and duration of furnace work. A slightly weaker trend was also found for duration of blue collar non-furnace work when lags of 25 or 30 years were applied in the analyses. However, several results indicated that the incidence of all cancers among the non- furnace workers decreased during the period of active employment. CONCLUSIONS: Furnace and non-furnace workers may have exposures that increase the incidence of several cancers. The low incidence of cancer among non-furnace workers during the period of ongoing exposure cannot be explained. As this study cannot identify any causal factors, the role of exposure to manganese remains unclear.